When copper (II) sulfate pentahydrate is heated, it undergoes a decomposition reaction to form copper (II) sulfate, water, and sulfur trioxide. The balanced equation for this reaction is:

CuSO4 * 5H2O --> CuSO4 + 5H2O + SO3

Here, one molecule of copper (II) sulfate pentahydrate decomposes to produce one molecule of copper (II) sulfate, five molecules of water, and one molecule of sulfur trioxide.